Telos Zephyr

Introduction

The Telos Zephyr is available in several configurations capable of mono and stereo operation, with and without internal terminal adapters.

All of NPR's Zephyrs have the capability to communicate with ISO MPEG Layer II & Musicam codecs as well as Layer III and G.722. They also contains a fan with a high-pitched wine that is a bit annoying. The following descriptions and instructions assume this configuration.

Telos has provided a handy Compatibility Chart which explains how their equipment works with other codecs. Other information is available from their Technical References page.

Operation

All controls are conveniently located on the front panel. Most information you need to see is displayed on a four line by twenty character, black on green screen, in the center of the front panel. In addition there are four LEDs that provide status. The active line on the display is the one with the square brackets around it.

To choose a menu item, press the No key to cycle through the choices and the Yes key to record your selection.

To enter numbers into a numeric field, press any of the number keys. Press the No key to erase the number to the left of the cursor and the Yes key to store the complete number.

To enter characters into an alpha-numeric field, press any of the number keys

There are four tasks that need to be accomplished to place a call.

Set the Transmit Mode
Set the Receive Mode
Set the Data Rate
Dial the Call

It is best to communicate with the distant end to establish the protocols for the call. While it is possible to make changes to all the parameters once the call is established, it is quicker if you start out with the correct information.

Transmit Mode

Zephyrs currently in production have eight possible transmit modes.

Mode	Connects With
L3 DUAL	Layer III codecs capable of Mono at 56 or 64K or Dual Mono at 112 or 128K.
L3 STEREO	Layer III Codecs capable of Stereo at 112 or 128K. Can also be used to send higher-quality Mono.
L3 JSTEREO	Layer III Codecs capable of Stereo at 112 or 128K. The two data channels are combined to provide better fidelity than the Stereo mode.
G.722	G.722 Codecs capable of Mono at 56 or 64K.
L2 MONO	Layer II codecs capable of Mono at 56 or 64K.
L2 MONO128	Layer II Codecs capable of Mono at 112 or 128K. The two data channels are combined to provide better fidelity than Mono mode.
L2 DUAL	Layer II Codecs capable of Dual Mono at 112 or 128K. Each channel is allotted half the available bit rate.
L2 JSTEREO	Layer II Codecs capable of Joint Stereo at 112 or 128K. The two audio channels share the available bit rate. Better fidelity than Stereo.

You can send two mono signals simultaneously between two Zephyrs. Both units should be configured as Mono/Dual Transmit and Stereo Receive. You can also send to two separate locations. The trick here is that the all Zephyrs must be using either layer III or G.722 and the Zephyr connected in the middle of the two single-channel units will set its speed according to the slowest of the two remote units. if you're only sending one mono signal but wish it to be the highest possible quality, set the encoder and decoder for J-STEREO. This will bond the two B Channels together for 128K mono transmission.

Receive Mode

The current production model Zephyr has four receive modes. Your receive mode must match the transmit mode of the other end.

Mode	Connects With
L3 MONO	Layer III codecs capable of Mono at 56 or 64K or Dual Mono at 112 or 128K.
L3 STEREO	Layer III Codecs capable of Stereo at 112 or 128K. Can also be used to send higher-quality Mono.
G.722	Layer III Codecs capable of Mono at 56 or 64K.
L2	Any Layer II Codec

Data Rate

There are four settings that select both the per-channel Data Rate and the Sample Rate. The Data Rate is for each B channel of the ISDN.

Rate	Connects With
56kbps 32khz	Other G.722 codecs at 56K or Layer III codecs at 56 to 112K.
64kbps 32khz	Other G.722 codecs at 64K or Layer III codecs at 64 to 128K.
56kbps 48khz	Other Layer II codecs at 56 or 112K.
64kbps 48khz	Other Layer II codecs at 64 or 128K.

Set the data rate before placing the call. The answering Zephyr will autobaud to match the calling Zephyr if the data path is capable of providing that rate. try it at 56 if it doesn't work at 64, one nice thing about the Zephyr is that you can change any parameter after the call has been placed.

Communications with an older Zephyr (without layer II) must be done with a sample rate of 32K. Communication with Layer II codecs is only supported with a sample rate of 48K.

Dial the Call

Press the Dial button.
Enter the number for the ISDN you are calling.
Press the Dial button again.
Repeat steps 1 to 3 for the second line if appropriate.

It's also possible to set up speed dials for often used sites that will properly configure the Zephyr and dial the necessary numbers. See the Zephyr Manual for more information.

Setup

A terminal adapter and NT1 are both built into the remote Zephyrs owned by NPR making them compact and easy to use for remote assignments. Use any two-conductor (or more) modular cable to connect the U interface (bottom jack) to the wall jack.

Setup involves entering the SPIDs and LDNs into the Zephyr as well as selecting what type of switch it is connected to. There are now three choices; P to P used for AT&T Custom and Natl I-1 used for everything else except for ETS-300 used for an Siemens switches.

Zephyr Trouble Shooting

A Zephyr will sometimes become stupid. Here's a list of their favorite faults and how to fix them.

Will Not Answer Incoming Calls

The first thing they forget is how to answer the phone. Check the configuration to ensure that auto-answer is selected.

Press the Util button until you see "AutoAnswer" on the top line of the display.
Press Yes.

If "AutoAnswer" is enabled The universal reset (power it off) has always solved this problem. Rule of thumb: "if it don't answer, turn it off."

You can also initiate what's called a warm boot by pressing the Help key followed by the # key.

No Audio is Transmitted

If the call has completed but you still can't hear any audio check the Lock indicator just below the receive meters.

It it is illuminated, the other end is not sending any audio.
If it is not illuminated, then the receiver is not configured the same as the remote transmitter.
1. Call the remote end on the phone.
2. Negotiate configuration; Data Rate and protocol.
3. Make each end's receive parameters match the other end's transmit parameters.
The same procedures apply if the far end can't hear what you're sending.

The Operation section describes how to change the various parameters.

Display Not Illuminated

This will occasionally happen on power up, it is annoying but is also easy to fix.

Power down the Zephyr.
Wait at least 10 seconds.
Hold down the No and Yes buttons while turning the power on.
Once power is returned
- Press the Up and Down arrows to adjust brightness.
- Press the No and Yes buttons to adjust contrast.
Once the display is where you want it, power off and on.

Display Contrast Unreadable

This will occasionally happen on power up, it is annoying but is also easy to fix. You can either use the method listed above or...

Look down on the display from a steep angle.
Press the Util button until you see "LCD Contrast" on the top line of the display.
Press the No button until the display is again readable.

The normal setting is 6.

Picture of the Back of the Zephyr

Conclusion

A stereo Zephyr with internal Terminal Adapter costs about $5K making it the winner for stereo transmission on a single BRI.

More information on the Zephyr codec is available from the Zephyr Home Page. You can also read Al Rieland's Switched Digital Audio Directory for Public Radio and read Jay Rose's Audiobahn, formerly known as ZephyrSpace.